At the Infant Primate Research Laboratory, there is frequently a need to establish the normalcy of an infant's developmental status. In human children, radiographs of the hand and wrist are commonly used by pediatricians to assess maturational status. Because the bones of the monkey and human hands develop in the same sequence and the morphology is strikingly similar, ossification standards that have been developed for use with humans can be used with macaques. What has been lacking is a standard that applies to specific age ranges in infant macaques. The two most frequently used methods to assess skeletal maturational status are the so-called "atlas method" and a quantitative scoring method (Tanner-Whitehouse Method, TW2). The first involves matching the radiograph in question to one pictured in an atlas and assigning the associated age. The second method requires that each bone center be scored and a total maturational score summed and plotted relative to age-base d de velopmental curves. The latter method requires extensive training before a technician can use it satisfactorily, although it allows the construction of numerically defined norms. We therefore scored by the TW2 method the serial hand/wrist radiographs of 60 infant pigtailed macaques (30 female, 30 male) done at seven ages, birth to 6 months. The 25th, 50th and 75th centiles were determined for each age and a representative male and female radiograph was chosen for each centile. An Atlas was then constructed from scanned images of the radiographs with accompanying descriptive notations. The atlas was tested using untrained observers, who came within acceptable error in assessing an animal's developmental age. The most recent use of the Atlas at the IPRL was in the evaluation of the skeletal developmental status of an infant with a chromosomal trisomy. FUNDING NIH grant RR00166. Wooldridge, K., Brazeau, E., and Newell-Morris, L. Hand and Foot Atlas for the Infant Macaca nemestrina. Seattle University of Washington, 1998.